JP2002075586A - Ventilation structure of plug cap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge a water storage tank, to simplify a mold and to reduce the defect rate. SOLUTION: In this ventilation structure, an insulation pipe 2 has a small- diameter peripheral face 23a whose diameter is reduced through a step 22 from a main peripheral face 21a on one end side, and a rib 24 projecting to the end along the small-diameter peripheral face 23a from the step 22. A rain cover 3 has a fitting tube 31 extending at a prescribed distance from the small- diameter peripheral face 23a and liquid-tightly fitting on the main peripheral face 21a, and atmosphere release hole 32c communicating with a gap between the fitting tube 31 and the small-diameter peripheral face 23a, while the rib 24 has a ventilation hole 24b opening toward the end and communicating with a plug hole E1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ventilation structure for a plug cap for guiding an electric wire to a spark plug in a plug hole.

[0002]

2. Description of the Related Art As a ventilation structure for a plug cap of this type, for example, one disclosed in Japanese Patent Application Laid-Open No. 9-7682 is known. The ventilation structure of this plug cap is shown in Figs.
As shown in FIG. 9, the ventilation line provided in the plug cap 1 allows the air to flow into the plug hole E1. That is, the plug cap 1 includes an insulating pipe 2 that guides the high-voltage wire E2 to a spark plug (not shown) located at the deepest portion in the plug hole E1 provided in the engine head E, and an upper side (one end side) of the plug hole E1. ), And a rubber rain cover 3 that covers the upper opening 2a of the insulating pipe 2 protruding from the opening E1a and guides the high-voltage electric wire E2 from the opening 2a side in a liquid-tight manner. I have. Although not shown, a rubber cap is provided on the lower side (the other end) of the insulating pipe 2 so as to be in close contact with the peripheral surface of the insulator in the spark plug.

[0003] The insulating pipe 2 has a reference end face 2 on its upper side.
A concave space is formed by the outer wall 2c and the inner wall 2d extending coaxially from b. The concave space is divided into two by a rib 2e, one of which is a water storage tank 2f and the other is a circulation tank 2g. The circulation tank 2g is provided with a ventilation hole 2h extending from the bottom surface, that is, the reference end surface 2b, into the plug hole E1. A flange 2i is formed on the insulating pipe 2 along the reference end surface 2b and close to the plug hole E1, and a groove 2j for holding the O-ring 4 is formed on the outer periphery of the flange 2i. Is formed. The insulating pipe 2 is formed by injection molding of a hard insulating resin material.

On the other hand, the rain cover 3 has a large diameter portion 3a fitted to the outer wall 2c and a small diameter portion 3b fitted to the inner wall 2d.
The small diameter portion 3b is provided with an air opening hole 3c connected to the water storage tank 2f. The annular flat surface 3d at the boundary between the large-diameter portion 3a and the small-diameter portion 3b is provided at a position spaced a predetermined distance from the upper end surface (one end surface) of the outer wall 2c. Further, the large diameter portion 3a is provided with a skirt portion 3e formed so as to surround an upper end surface (one end surface) and an outer peripheral surface of an annular convex portion E3 described later. The annular convex portion E3 has an opening E1a of the plug hole E1 in the engine head E.
, For example, to prevent the water applied to the engine head E from directly flowing into the plug hole E1.

In the ventilation structure of the plug cap constructed as described above, the opening 3c, the water storage tank 2f, the space between the upper end surface (one end surface) of each rib 2e and the annular flat surface 3d, the circulation tank 2g and the ventilation The hole 2h becomes a ventilation line, and the pressure in the plug hole E1 can be released to the atmosphere.
Therefore, for example, the plug hole E1
Even if the internal pressure changes, the pressure in the plug hole E1 can be kept constant. Also,
Since the air opening hole 3c and the ventilation hole 2h are located at alternate positions and the water storage tank 2f is provided on the side of the air opening hole 3c, for example, even if water is applied to the engine during car washing, the water is discharged to the plug hole E1. Never get inside.

[0006]

By the way, in the conventional plug cap ventilation structure, it is necessary to make the water storage tank 2f as wide as possible in order to increase the water storage effect. However, the thickness of the outer wall 2c surrounding the water storage tank 2f needs to be more than a predetermined thickness due to the material strength, and there is a demand from the engine side to reduce the diameter of the plug hole E1. . For this reason, there is a problem that it is difficult to widen the water storage tank 2f.

Further, by forming the water storage tank 2f and the circulation tank 2g, the mold for injection molding becomes complicated, and the outer wall 2c and the inner wall 2d are formed to have a thin cylindrical shape.
There is a problem that there is a high possibility that molding failure occurs due to resin filling failure (a so-called short shot) on the upper end surface (one end surface) of the outer wall 2c or the inner wall 2d.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a ventilation structure for a plug cap capable of enlarging a water storage tank, simplifying a mold, and reducing a defective rate. It is an issue.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an invention according to a first aspect of the present invention is directed to an insulating pipe for guiding an electric wire to a spark plug in a plug hole, an opening in the plug hole, and the opening. And a rain cover that covers an opening at one end of the insulating pipe located on the side of the plug cap, wherein the insulating pipe has a diameter reduced via a step from a main outer peripheral surface at one end thereof. A small-diameter outer peripheral surface is provided, and a rib protruding from the step portion to one end side along the small-diameter outer peripheral surface is provided. The rain cover extends at a predetermined distance from the small-diameter outer peripheral surface, and In addition to providing a fitting cylinder portion that fits in a liquid-tight manner on the outer peripheral surface, an air release hole is provided between the fitting cylindrical portion and the small-diameter outer peripheral surface, and the rib has an opening at one end thereof. Ventilation leading into the plug hole It is characterized in that the provided.

According to the first aspect of the present invention, the stepped portion of the insulating pipe is formed between the fitting cylindrical portion of the rain cover and the small-diameter outer peripheral surface of the insulating pipe, and the rib is formed circumferentially. It is possible to configure a water storage tank that is a partition in the direction. Further, the inside of the plug hole and the atmosphere side communicate with each other via the atmosphere opening hole of the rain cover, the water storage tank, and the ventilation hole of the rib.

In addition, since the conventional outer wall disappears, a portion corresponding to the outer wall becomes a water storage tank as it is. Therefore, the water storage tank can be made sufficiently large. In addition, since the thickness of the small-diameter outer peripheral portion can be increased and the capacity of the water storage tank can be somewhat sacrificed, it is possible to prevent a molding defect from occurring at one end surface of the small-diameter outer peripheral surface due to insufficient filling. Therefore, the defect rate can be reduced. Furthermore, since the outer wall is not required, the structure of the molding die is simplified, so that the cost can be reduced.

According to a second aspect of the present invention, in the first aspect of the present invention, the rib supports the fitting cylindrical portion of the rain cover from the inside.

According to the second aspect of the present invention, since the fitting cylindrical portion of the rain cover can be supported from the inside by the rib, even when the rain cover is formed of, for example, a material having flexibility, the fitting cylindrical portion is formed. Can be stably maintained, and the water tank can be prevented from narrowing.

According to a third aspect of the present invention, in the first or second aspect of the invention, the insulating pipe projects from the step portion to one end side along the small-diameter outer peripheral surface, and the fitting cylindrical portion of the rain cover is formed from the inside. It is characterized by having a supporting rib.

According to the third aspect of the present invention, the fitting cylindrical portion of the rain cover can be more stably held by the sub rib, and the capacity of the water storage tank is further stabilized. Also,
Since the water storage tank is divided into a plurality of parts by the sub ribs, the water that has entered enters the water storage tank that is farthest from the ventilation hole. Therefore, the probability that water enters the plug hole through the ventilation hole can be reduced.

According to a fourth aspect of the present invention, in the first, second or third aspect of the present invention, the fitting cylindrical portion of the rain cover is provided with:
It is characterized by providing a seal portion that is in close contact with the plug hole.

According to the fourth aspect of the present invention, since a sealing portion is provided in the fitting cylindrical portion of the rain cover so as to be in close contact with the inner surface of the plug hole, a sealing means such as an O-ring conventionally used becomes unnecessary. Therefore, cost can be reduced.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. However,
Elements common to those of the conventional example are denoted by the same reference numerals, and description thereof will be simplified.

The ventilation structure of the plug cap shown in this embodiment, as shown in FIGS. 1 to 3, allows the air to flow into the plug hole E1 by a ventilation line provided in the plug cap 10. In particular, the feature is that the water storage tank 5 is configured between the insulating pipe 2 and the rain cover 3.

That is, on the upper side (one end side) of the insulating pipe 2, a main outer peripheral surface 21a is formed, and a small-diameter outer peripheral surface 23a whose diameter is reduced from the main outer peripheral surface 21a via the step portion 22 is formed. Further, the rib 24 protruding upward from the step 22 along the small-diameter outer peripheral surface 23 a is formed by the step 22 and the small-diameter outer peripheral surface 2.
It is formed integrally with 3a. The small-diameter cylindrical portion 23 forming the small-diameter outer peripheral surface 23a is formed with an outlet 23b for extracting the high-voltage electric wire E2 from the upper end side.

The rib 24 is provided at a position corresponding to the outlet 23b, and has a height from the step 22 which is lower than the outlet 23b.
b is lower than the lower edge by a predetermined amount. The rib 24 has an outer peripheral surface 24a formed flush with the main outer peripheral surface 21a.
1 is supported from the inside. Furthermore, the rib 24
, A ventilation hole 24b is formed so as to penetrate vertically along the small-diameter outer peripheral surface 23a. And the ventilation hole 24b
Is opened at the upper end surface (one end surface) of the rib 24, and communicates with the inside of the plug hole E1 through the main cylindrical portion 21 and the flange portion 2i constituting the main outer peripheral surface 21a.

On the other hand, the rain cover 3 has a main outer peripheral surface 21.
a is formed with a fitting cylinder portion 31 which fits in a liquid-tight manner. The fitting cylindrical portion 31 extends in parallel with the small-diameter outer peripheral surface 23a from the step portion 22 to a position beyond the upper end surface of the rib 24 and not reaching the lower edge of the outlet 23b. ing. The upper side of the fitting cylindrical portion 31 is a reduced-diameter cylindrical portion 32 having a reduced-diameter inner peripheral surface 32a that fits in a liquid-tight manner on the small-diameter outer peripheral surface 23a. Then, the enlarged inner peripheral surface 31a and the reduced inner peripheral surface 3
The boundary with 2a is an annular plane 32b parallel to the step 22. The upper side of the reduced diameter cylindrical portion 32 is integrally closed by a top portion 33. Further, the reduced diameter cylindrical portion 32
At a position corresponding to the outlet 23b in
A guide tube portion 34 for holding the fluid-tight 2 is formed integrally. In addition, the reduced-diameter cylindrical portion 32 is provided at a position farthest from the rib 24 in the circumferential direction, that is, at a position farthest from the ventilation hole 24b, and an atmosphere opening hole connecting the inside of the fitting tube portion 31 and the atmosphere. 32c are formed.

The enlarged inner peripheral surface 31a and the smaller outer peripheral surface 2
A water storage tank 5 having the step 22 as a bottom surface, the annular flat surface 32b as a top surface, and the ribs 24 as partitions in the circumferential direction is formed between the storage tank 5 and the base plate 3a. The insulating pipe 2 and the rain cover 3 are made of the same material as that of the conventional example.

In the ventilation structure of the plug cap configured as described above, the air opening hole 32 of the rain cover 3 is provided.
c, between the upper end surface of the water storage tank 5 and the rib 24 and the annular flat surface 32b and the ventilation hole 24b of the rib 24 become a ventilation line, and the inside of the plug hole E1 and the atmosphere side communicate with each other through this ventilation line. . Then, since the existing outer wall 2c (see FIG. 7) disappears, the portion corresponding to the outer wall 2c directly leads to an increase in the capacity of the water storage tank 5. Therefore, the water storage tank 5 can be made sufficiently wide. In addition, since the thickness of the small-diameter cylindrical portion 23 can be increased and the capacity of the water storage tank 5 can be somewhat sacrificed, it is possible to prevent the occurrence of molding failure due to insufficient filling at the upper end surface of the small-diameter cylindrical portion 23. . Therefore, the defect rate can be reduced. Further, the elimination of the outer wall 2c simplifies the structure of the molding die, so that the cost can be reduced.

Further, since the fitting cylindrical portion 31 of the rain cover 3 can be supported from the inside by the outer peripheral surface 24a of the rib 24, the shape of the fitting cylindrical portion 31 formed of a flexible material made of rubber can be stabilized. Can be held in a stable manner. Therefore, the water storage tank 5 can be maintained in a wide state.

In the above-described embodiment, the fitting cylindrical portion 31 is supported from the inside by one rib 24. However, as shown in FIGS. 4 and 5, from the step portion 22 to the small-diameter outer peripheral surface 23a. The fitting cylindrical portion 31 may be configured to be held by the sub rib 25 protruding upward along the same.
That is, each sub-rib 25 is formed such that its outer peripheral surface 25 a is flush with the main outer peripheral surface 21 a and has the same height as the ribs 24 from the step portion 22. The sub-rib 25 shown in FIG. 4 is provided at a position exactly opposite to the rib 24 with respect to the center of the insulating pipe 2, and the sub-rib 25 shown in FIG. 5 is provided at a position equally divided into four in the circumferential direction. .

When such sub-ribs 25 are provided, the air opening holes 32c of the rain cover 3, the water storage tanks 5,
Between the upper end surface of the sub-rib 25 and the annular flat surface 32b;
4 and the ventilation hole 24b between the upper end surface and the annular flat surface 32b become a ventilation line. Then, the outer peripheral surface 25 of the sub rib 25
With a, the fitting cylinder portion 31 can be held more stably. Further, when the water storage tank 5 is divided into a plurality of parts by two or more sub-ribs 25, water is first stored in the water storage tank 5 farthest from the ventilation hole 24b, and the rib 2
Since the water storage tank 5 adjacent to 4 functions as a drain tank, the probability that water enters the plug hole E1 through the ventilation hole 24b can be extremely reduced. In addition, you may comprise so that the ventilation hole 24b may be provided in the sub rib 25.

As shown in FIG. 6, the main outer peripheral surface 21a
And fitting groove 31 for O-ring 4 (see FIG. 1).
, And the fitting cylindrical portion 31 may be provided with a seal portion 31b that is in close contact with the plug hole E1. The seal portion 31b protrudes in an arc shape in cross section from the outer peripheral surface of the fitting tube portion 31, presses against the inner peripheral surface of the plug hole E1, and presses the enlarged inner peripheral surface 31a against the main outer peripheral surface 21a by the reaction force. It has become. Therefore, the cost can be reduced by eliminating the O-ring 4, and the liquid tightness between the fitting tube portion 31 and the main outer peripheral surface 21a can be improved.

[0029]

According to the first aspect of the present invention, between the fitting cylindrical portion of the rain cover and the small-diameter outer peripheral surface of the insulating pipe,
It is possible to form a water storage tank in which the step portion of the insulating pipe is used as the bottom surface and the rib is partitioned in the circumferential direction. Further, the inside of the plug hole and the atmosphere side communicate with each other via the atmosphere opening hole of the rain cover, the water storage tank, and the ventilation hole of the rib.

Further, since the conventional outer wall is eliminated, a portion corresponding to the outer wall becomes a water storage tank as it is. Therefore, the water storage tank can be made sufficiently large. In addition, since the thickness of the small-diameter outer peripheral portion can be increased and the capacity of the water storage tank can be somewhat sacrificed, it is possible to prevent a molding defect from occurring at one end surface of the small-diameter outer peripheral surface due to insufficient filling. Therefore, the defect rate can be reduced. Furthermore, since the outer wall is not required, the structure of the molding die is simplified, so that the cost can be reduced.

According to the second aspect of the present invention, since the fitting cylindrical portion of the rain cover can be supported from the inside by the rib, even if the rain cover is formed of a material having flexibility, for example, the fitting cylindrical portion can be supported. Can be stably maintained, and the water tank can be prevented from narrowing.

According to the third aspect of the present invention, the fitting rib portion of the rain cover can be more stably held by the sub rib, and the capacity of the water storage tank is further stabilized. Also,
Since the water storage tank is divided into a plurality of parts by the sub ribs, the water that has entered enters the water storage tank that is farthest from the ventilation hole. Therefore, the probability that water enters the plug hole through the ventilation hole can be reduced.

According to the fourth aspect of the present invention, since the sealing portion that is in close contact with the inner surface of the plug hole is provided in the fitting cylindrical portion of the rain cover, a sealing means such as an O-ring conventionally used becomes unnecessary. Therefore, cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a ventilation structure of a plug cap shown as one embodiment of the present invention.

FIG. 2 is a sectional view of a main part showing an insulating pipe in the ventilation structure of the plug cap.

FIG. 3 is a plan view showing an insulating pipe in the ventilation structure of the plug cap.

FIG. 4 is a plan view showing an example in which one sub-rib is provided on an insulating pipe in the ventilation structure of the plug cap.

FIG. 5 is a plan view showing an example in which three sub-ribs are provided on an insulating pipe in the ventilation structure of the plug cap.

FIG. 6 is a cross-sectional view of a main part showing an example in which a seal portion is provided on a rain cover in the ventilation structure of the plug cap.

FIG. 7 is a sectional view of a main part of a ventilation structure of a plug cap shown as a conventional example.

FIG. 8 is a sectional view of a main part showing an insulating pipe in a ventilation structure of the plug cap.

FIG. 9 is a plan view showing an insulating pipe in the ventilation structure of the plug cap.

[Explanation of symbols]

 Reference Signs List 2 Insulation pipe 2a Opening 3 Rain cover 21a Main outer peripheral surface 22 Step 23a Small outer peripheral surface 24 Rib 24b Ventilation hole 25 Sub-rib 31 Fitting tube 31b Seal 32c Open to atmosphere E1 Plug hole E1a Opening E2 High voltage electric wire (electric wire) )

Claims (4)

[Claims] 1. An insulating pipe for guiding an electric wire to a spark plug in a plug hole, and a rain cover for covering an opening of the plug hole and an opening on one end side of the insulating pipe located on the opening side. A ventilation structure for a plug cap, wherein the insulating pipe is provided with a small-diameter outer peripheral surface that is reduced in diameter from a main outer peripheral surface on one end side via a step portion, and is provided on one end side along the small-diameter outer peripheral surface from the step portion. A protruding rib is provided, and the rain cover is provided with a fitting cylinder portion extending at a predetermined distance from the small-diameter outer peripheral surface and fitted to the main outer peripheral surface in a liquid-tight manner. A vent opening connected to the cylindrical portion and the small-diameter outer peripheral surface, wherein the rib has an opening at one end thereof and a ventilation hole connected to the inside of the plug hole; Construction. 2. The ventilation structure for a plug cap according to claim 1, wherein the rib supports the fitting cylindrical portion of the rain cover from the inside. 3. The ventilation structure for a plug cap according to claim 1, wherein the insulating pipe has a sub rib protruding from the step portion to one end side along the small-diameter outer peripheral surface to support the fitting cylindrical portion of the rain cover from the inside. The ventilation structure of the plug cap characterized by having provided. 4. The ventilation structure for a plug cap according to claim 1, wherein the fitting portion of the rain cover is provided with a sealing portion that is in close contact with the plug hole. Construction.